In response to a perceived object, such as an object seen or heard, people exhibit a perceptual reaction, such as making a facial expression or gesturing to express emotion. After perceiving the same object a plurality of times, the perceptual reaction of a person to the object may differ from the first time, therefore it is difficult to predict the perceptual reaction of the person simply based on skill or attributes such as gender and age.
Conventionally a technique to estimate human emotion by analyzing perceptual reaction is known. Such a technique is sometimes used for estimating whether a user has an interest, concern or eagerness to receive information (hereafter collectively referred to as “interest”) about the content, for example, based on the expression or the like of a user who is looking at the content, such as images, distributed by a server. Thereby the interest of the user about the content can be known, and the result can be fed back for improvement of the content.